Week 10

Week 10: Describe the roles of the photoreceptor cells. (3 Marks)

The retina consists of two photoreceptor cells: cones and rods.

Cones have a light sensitive pigment called photopsin and rods have a light sensitive pigment called rhodopsin. They have different roles because the photopsin in cones when triggered by light (opsin) stimulate colour vision and acute (fine) vision. Rods when triggered by opsin stimulate night vision (or vision in dim light) and detection of basic movement.  The main role of the photoreceptor cells is to convert light energy into electrochemical energy for the brain (primary visual cortex) to translate the information. The photoreceptors collectively when stimulated by light have 3 main roles:

1. They absorb light energy (opsin)
2. They convert light energy (opsin) into electrochemical energy, generating a nerve impulse
3. They transmit this nerve impulse towards the bipolar cells of the retina.


Marking Criteria:

Criteria	Mark
Provides 3 characteristics and features of the role of the photoreceptors and is able to link these roles for the brain to interpret the information.	3
Provides 2 characteristics and features of the role of the photoreceptors	2
Identifies the photoreceptors: cones and rods and/or provides 1 characteristic and feature of the role of the photoreceptors	1